This invention relates to a multiplexer and more particularly to a multiplexer which is capable of selectively connecting one of a plurality of signals or channels on separate leads connected thereto to a common output/input lead, or conversely connecting a signal on said output/input lead to a desired one of said plurality of separate leads. The multiplexer is designed so that it can accommodate signals of much higher voltage than that of the logic supply rails used to energize and operate the circuitry. Normally, prior art multiplexers of this type have only been able to accommodate signals within the range of the logic circuit's supply voltage which is typically .+-.15 volts. The analog signal voltage range of the present multiplexer is limited only by the breakdown voltage of the FET transistors used in the signal processing (or output) channels, and hence can be many times the aforementioned range of the circuit supply voltage. Also, the circuit is designed to have an extremely low "on" resistance so that signals being processed do not suffer undue attenuation, and the "off" resistance is extremely high to prevent leakage between channels. Further, provision may be made for rapidly switching off a channel in response to a dump signal.